import {
    CreateEventBusCommand,
    DeleteEventBusCommand,
    DescribeEventBusCommand,
    DeleteRuleCommand,
    ListEventBusesCommand,
    ListRulesCommand,
    ListTargetsByRuleCommand,
    PutRuleCommand,
    PutEventsCommand,
    PutTargetsCommand,
    RemoveTargetsCommand,
    type EventBridgeClient,
    type EventBus,
    type Rule,
    type Target,
} from '@aws-sdk/client-eventbridge'
import {AddPermissionCommand, type LambdaClient} from '@aws-sdk/client-lambda'
import {awsEventBridgeSchema} from '../cloud-spi/eventbridgeSchema'
import {ValidationError} from '../cloud-spi/errors'
import type {
    CloudResource,
    CloudServiceAdapter,
    CloudServiceDescriptorOverride,
    CreateResourceInput,
    EventBridgeRuleInput,
    EventBridgeRuleOverview,
    EventBridgeRuleTarget,
    EventBridgePutEventInput,
    EventBridgePutEventResult,
    ResourceQuery,
    ServiceSchema,
} from '../cloud-spi/types'

const EVENT_BUS_PREFIX = 'event-bus:'

/** AWS EventBridge event buses through the provider-neutral Events category. */
export class AwsEventBridgeAdapter implements CloudServiceAdapter {
    readonly cloud = 'aws' as const
    readonly service = 'events' as const

    constructor(
        private readonly eventbridge: EventBridgeClient,
        private readonly lambda: LambdaClient,
    ) {}

    schema(): ServiceSchema {
        return awsEventBridgeSchema()
    }

    descriptorOverride(): CloudServiceDescriptorOverride {
        return {displayName: 'EventBridge'}
    }

    async list(query: ResourceQuery = {}): Promise<CloudResource[]> {
        const eventBuses: EventBus[] = []
        let nextToken: string | undefined
        do {
            const response = await this.eventbridge.send(new ListEventBusesCommand({NextToken: nextToken}))
            eventBuses.push(...(response.EventBuses ?? []))
            nextToken = response.NextToken
        } while (nextToken)

        return filterBySearch(eventBuses.map(eventBusResource), query.search)
    }

    async get(id: string): Promise<CloudResource | null> {
        const name = eventBusName(id)
        try {
            return eventBusResource(await this.eventbridge.send(new DescribeEventBusCommand({Name: name})))
        } catch (error) {
            if (isNotFound(error)) return null
            throw error
        }
    }

    async create(input: CreateResourceInput): Promise<CloudResource> {
        const name = requiredValue(input.values.name, 'name')
        const description = stringValue(input.values.description) || undefined
        const response = await this.eventbridge.send(new CreateEventBusCommand({Name: name, Description: description}))

        return eventBusResource({Name: name, Arn: response.EventBusArn, Description: description})
    }

    async delete(id: string): Promise<void> {
        await this.eventbridge.send(new DeleteEventBusCommand({Name: eventBusName(id)}))
    }

    async listEventBridgeRules(eventBusId: string): Promise<EventBridgeRuleOverview[]> {
        const busName = eventBusName(eventBusId)
        const rules: Rule[] = []
        let nextToken: string | undefined
        do {
            const response = await this.eventbridge.send(new ListRulesCommand({
                ...eventBusInput(busName),
                NextToken: nextToken,
            }))
            rules.push(...(response.Rules ?? []))
            nextToken = response.NextToken
        } while (nextToken)

        return Promise.all(rules.filter((rule) => Boolean(rule.Name)).map(async (rule) => {
            const name = rule.Name as string
            return ruleOverview(rule, busName, await this.listTargets(name, busName))
        }))
    }

    async createEventBridgeRule(eventBusId: string, input: EventBridgeRuleInput): Promise<EventBridgeRuleOverview> {
        const busName = eventBusName(eventBusId)
        const name = requiredValue(input.name, 'name')
        const targetInput = ruleInput(input)
        const response = await this.eventbridge.send(new PutRuleCommand({
            Name: name,
            ...eventBusInput(busName),
            ...(targetInput.scheduleExpression ? {ScheduleExpression: targetInput.scheduleExpression} : {}),
            ...(targetInput.eventPattern ? {EventPattern: targetInput.eventPattern} : {}),
            State: targetInput.state,
            ...(targetInput.description ? {Description: targetInput.description} : {}),
        }))
        const arn = response.RuleArn
        if (!arn) throw new ValidationError(`EventBridge rule ${name} did not return an ARN`)

        await this.eventbridge.send(new PutTargetsCommand({
            Rule: name,
            ...eventBusInput(busName),
            Targets: input.targets.map((target) => ({Id: target.id, Arn: target.arn})),
        }))
        await Promise.all(input.targets.filter((target) => isLambdaArn(target.arn)).map((target) =>
            this.lambda.send(new AddPermissionCommand({
                FunctionName: target.arn,
                StatementId: permissionStatementId(busName, name, target.id),
                Action: 'lambda:InvokeFunction',
                Principal: 'events.amazonaws.com',
                SourceArn: arn,
            })),
        ))
        return {
            name,
            busName,
            busId: `${EVENT_BUS_PREFIX}${busName}`,
            arn,
            ...targetInput,
            targets: input.targets,
        }
    }

    async deleteEventBridgeRule(eventBusId: string, ruleName: string): Promise<void> {
        const busName = eventBusName(eventBusId)
        const name = requiredValue(ruleName, 'ruleName')
        const targets = await this.listTargets(name, busName)
        const targetIds = targets.map((target) => target.Id).filter((id): id is string => Boolean(id))
        if (targetIds.length > 0) {
            await this.eventbridge.send(new RemoveTargetsCommand({Rule: name, ...eventBusInput(busName), Ids: targetIds}))
        }
        await this.eventbridge.send(new DeleteRuleCommand({Name: name, ...eventBusInput(busName)}))
    }

    async putEventBridgeEvent(eventBusId: string, input: EventBridgePutEventInput): Promise<EventBridgePutEventResult> {
        const source = requiredValue(input.source, 'source')
        const detailType = requiredValue(input.detailType, 'detailType')
        const detail = requiredValue(input.detail, 'detail')
        try {
            const parsed: unknown = JSON.parse(detail)
            if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed)) throw new Error('not an object')
        } catch {
            throw new ValidationError('detail must be a JSON object')
        }
        const response = await this.eventbridge.send(new PutEventsCommand({Entries: [{
            EventBusName: eventBusName(eventBusId), Source: source, DetailType: detailType, Detail: detail,
            ...(input.resources?.length ? {Resources: input.resources} : {}),
        }]}))
        const entry = response.Entries?.[0]
        return {eventId: entry?.EventId ?? null, errorCode: entry?.ErrorCode ?? null, errorMessage: entry?.ErrorMessage ?? null}
    }

    private async listTargets(ruleName: string, busName: string): Promise<Target[]> {
        const targets: Target[] = []
        let nextToken: string | undefined
        do {
            const response = await this.eventbridge.send(new ListTargetsByRuleCommand({
                Rule: ruleName,
                ...eventBusInput(busName),
                NextToken: nextToken,
            }))
            targets.push(...(response.Targets ?? []))
            nextToken = response.NextToken
        } while (nextToken)
        return targets
    }
}

function eventBusResource(eventBus: EventBus): CloudResource {
    const name = eventBus.Name ?? ''
    return {
        id: `${EVENT_BUS_PREFIX}${name}`,
        name,
        cloud: 'aws',
        service: 'events',
        type: 'event-bus',
        region: regionFromArn(eventBus.Arn),
        createdAt: eventBus.CreationTime?.toISOString() ?? null,
        status: null,
        metadata: {
            provider: 'aws',
            eventsService: 'eventbridge',
            arn: eventBus.Arn,
            description: eventBus.Description,
            policy: eventBus.Policy,
            lastModifiedAt: eventBus.LastModifiedTime?.toISOString() ?? null,
        },
    }
}

function eventBusName(id: string): string {
    const name = id.startsWith(EVENT_BUS_PREFIX) ? id.slice(EVENT_BUS_PREFIX.length) : ''
    if (!name) throw new ValidationError(`Unknown EventBridge event bus id: ${id}`)
    return name
}

function requiredValue(value: unknown, field: string): string {
    const result = stringValue(value)
    if (!result) throw new ValidationError(`${field} is required`)
    return result
}

function stringValue(value: unknown): string {
    return typeof value === 'string' ? value.trim() : ''
}

function filterBySearch(resources: CloudResource[], search?: string): CloudResource[] {
    const normalized = search?.trim().toLowerCase()
    if (!normalized) return resources
    return resources.filter((resource) => resource.name.toLowerCase().includes(normalized))
}

function regionFromArn(arn?: string): string | null {
    return arn?.split(':')[3] || null
}

function isNotFound(error: unknown): boolean {
    if (!error || typeof error !== 'object') return false
    const value = error as {name?: string; $metadata?: {httpStatusCode?: number}}
    return value.name === 'ResourceNotFoundException' || value.$metadata?.httpStatusCode === 404
}

function eventBusInput(busName: string): {EventBusName?: string} {
    return busName === 'default' ? {} : {EventBusName: busName}
}

function ruleInput(input: EventBridgeRuleInput): Pick<EventBridgeRuleOverview, 'scheduleExpression' | 'eventPattern' | 'state' | 'description'> {
    const scheduleExpression = stringValue(input.scheduleExpression)
    const eventPattern = stringValue(input.eventPattern)
    if (Boolean(scheduleExpression) === Boolean(eventPattern)) {
        throw new ValidationError('exactly one of scheduleExpression or eventPattern is required')
    }
    if (eventPattern) {
        try {
            JSON.parse(eventPattern)
        } catch {
            throw new ValidationError('eventPattern must be a JSON string')
        }
    }
    if (!Array.isArray(input.targets) || input.targets.length === 0) throw new ValidationError('at least one target is required')
    const targetsValid = input.targets.every((target) => requiredValue(target.id, 'target.id') && requiredValue(target.arn, 'target.arn'))
    if (!targetsValid) throw new ValidationError('target id and arn are required')
    const state = input.state ?? 'ENABLED'
    if (state !== 'ENABLED' && state !== 'DISABLED') throw new ValidationError('state must be ENABLED or DISABLED')
    return {
        ...(scheduleExpression ? {scheduleExpression} : {}),
        ...(eventPattern ? {eventPattern} : {}),
        state,
        ...(stringValue(input.description) ? {description: stringValue(input.description)} : {}),
    }
}

function ruleOverview(rule: Rule, busName: string, targets: Target[]): EventBridgeRuleOverview {
    return {
        name: rule.Name ?? '',
        busName,
        busId: `${EVENT_BUS_PREFIX}${busName}`,
        arn: rule.Arn ?? null,
        ...(rule.ScheduleExpression ? {scheduleExpression: rule.ScheduleExpression} : {}),
        ...(rule.EventPattern ? {eventPattern: rule.EventPattern} : {}),
        state: rule.State === 'DISABLED' ? 'DISABLED' : 'ENABLED',
        ...(rule.Description ? {description: rule.Description} : {}),
        targets: targets.flatMap((target) => target.Id && target.Arn ? [{id: target.Id, arn: target.Arn}] : []),
    }
}

function isLambdaArn(arn: string): boolean {
    return arn.split(':')[2] === 'lambda'
}

function permissionStatementId(busName: string, ruleName: string, targetId: string): string {
    return `floci-events-${busName}-${ruleName}-${targetId}`.replace(/[^A-Za-z0-9_-]/g, '_').slice(0, 100)
}